1. Field of the Invention
The invention relates to thermal management of pressurized fuel cell systems with compressor/expander systems.
2. Description of Related Art
The general arrangement of a pressurized fuel cell system is disclosed in U.S. Pat. No. 6,521,366 to Lamm et al. The fuel cell system has an anode chamber and a cathode chamber separated from one another by a proton-conducting membrane, also known as a proton exchange membrane (PEM). A cathode supply line supplies gas containing oxygen to the cathode chamber, and an anode supply line supplies a liquid coolant/fuel mixture to the anode chamber. The anode chamber is located in an anode circuit that includes a gas separator and a pump, and with a cooler and a water separator being located in the separated gas flow from the gas separator in the flow direction.
In a further arrangement of a fuel cell power system disclosed in U.S. Pat. No. 6,551,732 to Xu, the fuel cell processes air through the cathode to yield a cathode effluent stream. The fuel cell power system further includes a fuel processor for converting an inlet fuel stream of hydrogen- and carbon-containing fuels, utilizing a stream of oxygen-containing gas and water vapor, to a processed fuel stream of hydrogen molecules for feeding into the fuel cell anode. The system then feeds a substantial portion of the cathode effluent stream to the fuel processor as the oxygen-containing gas and water vapor for converting the fuel stream into hydrogen. A portion of the cathode effluent stream is also available for burning with a substantially hydrogen depleted gas exiting the anode in a combustor, the exhaust of the combustor being then passed through an expander for powering an input air compressor.
The fuel cell integral to these systems generates a substantial amount of “waste” heat, as do other components such as the combustor. Removal of this waste heat is generally accomplished by a cooling system, or the heat energy is simply expelled to the environment. It would be advantageous to increase the efficiency of the fuel cell system by reducing the “waste” and converting more of the heat generated by the fuel cell and other system components into useful work, thereby increasing the efficiency of the system.